In a variety of commercial and industrial settings, it is necessary to remove all or a portion of a substance from a fluid, i.e., a gas or a liquid, before the fluid can be used for a particular purpose. For example, before contaminated water can be drunk or contaminated air can be breathed, any hazardous contaminants must be removed. Likewise, before compressed air can be used, for example to drive power tools, any water vapor should be removed. If the water vapor is not removed, it may condense in the piping or in the tools, causing rust or otherwise corroding the equipment.
Many types of devices are available to remove a substance from a fluid. One particularly effective class of devices characteristically comprises an apparatus which directs a flow of the fluid through a sorbent material. A sorbent material is one which sorbs, i.e., absorbs or adsorbs, certain substances. Usually, sorbent materials are riddled with microscopic pores interconnected with one another, allowing the fluid to flow through the pores. Further, the sorbent material is typically in the form of a bed of particles of the sorbent material contained in a cylindrical chamber. During a sorbing phase, the fluid containing the substance is pumped into one end of the chamber and then passed through the sorbent particle bed where at least a portion of the substance is sorbed by the sorbent material. The fluid, now substantially free or at least containing less of the substance, is then removed from the other end of the chamber.
To extend the useful life of these sorbing apparatus, the sorbent bed is periodically regenerated, i.e., stripped of the substances that it has sorbed from the fluid. During a regenerating phase, a heated and/or substance-free fluid is flushed through the sorbent bed, purging the substance from the sorbent particles. This purging fluid, now containing much of the substance previously sorbed by the sorbent bed, is then exhaustedfrom the chamber. Once the sorbent bed is sufficiently free of the substance, the fluid containing the substance is again pumped through the chamber and the regenerated sorbent bed continues sorbing the substance from the fluid. The sorbing apparatus can continue cycling between the sorbing phase and the regenerating phase for an extended period.
As effective as these apparatus are, they nevertheless have several undesirable characteristics. For example, many sorbent materials, including alumina, are relatively soft and may crumble or otherwise disintegrate as the fluid flows through the sorbent bed and causes the sorbent particles to collide with one another. Many sorbent materials further disintegrate when they are exposed to heat and water, both of which are often present in the sorbent bed because heat is naturally produced during the sorbing phase and because the substance sorbed by the sorbent material frequently is water. A disintegrating sorbent material may generate significant quantities of sorbent dust, i.e.,small fragments of the sorbent particles which are swept along with the fluid flowing through the sorbent bed. This sorbent dust is extremely abrasive and may damage any downstream pipes and valves if it escapes the chamber.
Another undesirable characteristic of conventional sorbing apparatus is that many sorbent materials, including alumina and molecular sieve, may become clogged if the fluid contains a hydrocarbon such as oil. For example, if the sorbing apparatus is removing water vapor from compressed air, oil vapor from the compressor may also find its way into the air. While the pores of the sorbent material are very small, the molecules of oil as well as the molecules of water are even smaller. Consequently, both the water molecules and the oil molecules penetrate the pores of the sorbent material and are then sorbed by the sorbent material. However, not all of the oil which penetrates the sorbent material is removed during the regenerating phase. Consequently, over a period of time, the sorbent material becomes more and more clogged with oil and less and less able to remove the water vapor from the air.